<!doctype html> 
<html ng-app='text'> 
<head> 
    <meta charset="utf-8"> 
    <title></title> 
    <script type="text/javascript">


    class leo {
        constructor(x,y){
            this.x = x;
        }
        toHaha(){
            alert(this.x);
        }
    };

    new leo(2,3).toHaha();
    /*
    var a = {
        x:20,
        c:30
    };
    */
    //alert(Object.is(NaN,NaN))
   // alert(Symbol() === Symbol());
    //symbol 
   // var a = Symbol.for('abc');
    //var b = Symbol.for('abc')
    //alert(a == b);
    var a = {b:20};
    a[Symbol()] = 30;
    a[Symbol()] = 20;
    a[Symbol()] = 10;
    // console.log(a);
    /*
    for(var i in a){
        console.log(i)
    }
    */
  //  console.log();
    Object.getOwnPropertySymbols(a).find(function (i,b,k){
        //i == Symbol; 
        //b == index;
        //k == [zijis]
        //console.log(i)
       // console.log(a[k[b]])
    })

    </script>
</head>
<body>

</body>
</html>